WAFER CONTAINER WITH DOOR GUIDE AND SEAL

Abstract

A wafer container that reduces or alleviates one or more of the problems associated with excessive container wall deflection due to loading and excessive particulate generation, particularly as those problems are experienced with containers for 450 mm diameter and larger wafers. The container has an enclosure and door with interlocking features to enable transfer of tension load to the door to minimize deflection of container surfaces. The container may include a gasketing arrangement compatible with the interlock feature. The container may include a removable door guide that improves centering of the door during door installation, and that is made of low particle generating material to reduce particulates.

Claims

1. A front opening container for semiconductor wafers comprising: an enclosure portion including a top wall, a bottom wall, a pair of side walls, a back wall, and a door frame opposite the back wall, the door frame defining a front opening, the door frame having a plurality of intersecting side walls forming a plurality of door frame corners, each side wall defining a ramped portion intermediate adjacent door frame corners; a door removably received in the door frame for closing the front opening, the door comprising a body portion presenting a plurality of intersecting peripheral faces; a plurality of door guides, each door guide disposed on a separate one of the peripheral faces such that each door guide is engaged with a separate one of the ramped portions of the door frame when the door is received in the door frame.

2. The container of claim 1, wherein the door frame defines an outwardly facing recess inward from each ramped portion and extending parallel with a front edge of the front opening, and wherein the each door guide defines an edge, the edge of the door guide being engaged in the recess to interlock the door with the enclosure portion when the door is received in the door frame.

3. The container of claim 2, wherein the recess is generally v-shaped and presents an engagement surface, and wherein the edge of the door guide has an engagement surface conformingly disposed so as to confront the engagement surface of the recess when the edge of the door guide is received in the recess.

4. The container of claim 1, wherein each of the plurality of peripheral faces of the body portion defines a door guide recess, and wherein a separate one of the door guides is received in each of the door guide recesses.

5. The container of claim 4, wherein each of the door guides has at least one engagement structure, the at least one engagement structure received by a corresponding engagement structure in the door guide recess.

6. The container of claim 5, wherein the at least one engagement structure is an engagement tab, and the corresponding engagement structure is an aperture.

7. The container of claim 1, wherein the door includes an elastomeric seal extending around a periphery of the door, the elastomeric seal engaging structure on the door frame when the door is received in the door frame to hermetically seal the enclosure portion.

8. The container of claim 1, further comprising a wafer cushion disposed on a rear side of the door.

9. The container of claim 1, wherein the door guide is made from a low particle generating material.

10. The container of claim 9, wherein the low particle generating material includes acetal or PBT.

11. A front opening container for semiconductor wafers comprising: an enclosure portion including a top wall, a bottom wall, a pair of side walls, a back wall, and a door frame opposite the back wall, the door frame defining a front opening, the door frame defining a forwardly facing recess extending around an inner periphery of the door frame parallel with a front edge of the door frame; a door removably received in the door frame for closing the front opening, the door comprising a body portion presenting a rear side and a gasket assembly disposed on the rear side, the gasket assembly including a gasket frame and a gasket, the gasket frame defining an elongate projection extending around a periphery of the door, the gasket being retained between the gasket frame and the body portion and including a laterally projecting sealing portion, wherein the projection of the gasket frame is received in the recess of the door frame to interlock the door with the door frame when the door is received in the door frame, and wherein the laterally projecting portion of the gasket engages and seals against a side wall of the door frame when the door is received in the door frame.

12. The container of claim 11, wherein the gasket assembly includes an integrally formed wafer cushion.

13. The container of claim 12, wherein the gasket assembly substantially covers the entire rear side of the body portion of the door.

14. The container of claim 11, wherein the gasket is over-molded on the gasket frame.

15. The container of claim 11, wherein the forwardly facing recess is generally v-shaped and presents an engagement surface, and wherein the projection of the gasket assembly has an engagement surface conformingly disposed so as to confront the engagement surface of the recess when the projection is received in the recess.

16. A front opening container for semiconductor wafers comprising: an enclosure portion including a top wall, a bottom wall, a pair of side walls, a back wall, and a rectangular door frame opposite the back wall, the door frame defining a front opening, the door frame defined by side walls extending between corners of the rectangular door frame, each side wall defining a ramped portion intermediate adjacent corners; a rectangular door removably received in the door frame for closing the front opening, the door comprising a body portion presenting four intersecting peripheral faces; a plurality of door guides, each door guide disposed on a separate one of the peripheral faces such that each door guide is engaged with a separate one of the ramped portions of the door frame when the door is received in the door frame.

17. The container of claim 16, wherein the door frame defines an outwardly facing recess inward from each ramped portion and extending parallel with a front edge of the front opening, and wherein the each door guide defines an engagement structure, the engagement structure of the door guide being engaged in the recess to interlock the door with the enclosure portion when the door is received in the door frame.

18. The container of claim 17, wherein the recess is generally v-shaped and presents an engagement surface, and wherein the engagement structure of the door guide has an engagement surface conformingly disposed so as to confront the engagement surface of the recess when the engagement structure of the door guide is received in the recess.

19. The container of claim 16, wherein each of the plurality of peripheral faces of the body portion defines a door guide recess, and wherein a separate one of the door guides is received in each of the door guide recesses.

20. The container of claim 19, wherein each of the door guides has at least one engagement structure, the at least one engagement structure received by a corresponding engagement structure in the door guide recess.

21. The container of claim 16, wherein the door guide is made from a low particle generating material.

22. The container of claim 21, wherein the low particle generating material includes acetal or PBT.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0048] The embodiments of the present invention may be more completely understood in consideration of the following detailed description of various embodiments in connection with the accompanying drawings, in which:

[0049] FIG. 1 is an exploded front isometric view of a front-opening wafer container according to an embodiment of the invention;

[0050] FIG. 2 is an exploded isometric view of an embodiment of a front door assembly for the container of FIG. 1;

[0051] FIG. 3 is an exploded isometric view of another embodiment of a front door assembly for the container of FIG. 1;

[0052] FIG. 4 is a fragmentary cross-sectional view of the container of FIG. 1, depicting the front door assembly engaged in the door frame of the enclosure portion;

[0053] FIG. 5 is an exploded view of a front door assembly, depicting the wafer cushion assembly registered for placement on the door body;

[0054] FIG. 6 is an isometric view of a front door cushion assembly with the cushion material extending across substantially the entirety of the inside facing surface of the door;

[0055] FIG. 7 is an isometric view of the rear side of the front door cushion assembly of FIG. 6;

[0056] FIG. 8 is a cross-sectional view taken through a corner of a container portion and front door assembly with the front door assembly in a first stage of insertion in the door frame;

[0057] FIG. 9 a cross-sectional view of the corner of the container portion and front door assembly depicted in FIG. 8, with the front door assembly in a second stage of insertion in the door frame;

[0058] FIG. 10 a cross-sectional view of the corner of the container portion and front door assembly depicted in FIG. 8, with the front door assembly fully seated in the door frame;

[0059] FIG. 11 is a fragmentary cross-sectional view taken at section 11-11 of FIG. 1;

[0060] FIG. 12 is a fragmentary cross-sectional view of a door engaged with a door frame of a container portion according to an alternative embodiment of the invention;

[0061] FIG. 13 is an exploded front isometric view of a front-opening wafer container according to another embodiment of the invention;

[0062] FIG. 14 is an assembled front isometric view of the front-opening wafer container of FIG. 13;

[0063] FIG. 15 is an isometric view of the bottom edge of the door frame of the container of FIG. 13, depicting the ramped door guide engagement portions and interlocking feature;

[0064] FIG. 16 is an isometric view of the rear side of the door assembly of the wafer container of FIG. 13;

[0065] FIG. 17 is a detail view of one of the side door guides of the door assembly of FIG. 16;

[0066] FIG. 18 is a detail view of the top door guide of the door of FIG. 16;

[0067] FIG. 19 is a partial cross-sectional view through the bottom door guide taken at section 19-19 of FIG. 14;

[0068] FIG. 20 is an isometric view of the rear side of the door of FIG. 16, with the door guides omitted to show the door guide engaging apertures;

[0069] FIG. 21 is a partial isometric view of the side of the door of FIG. 16, depicting the door guide in a position registered for insertion in the receiving recess;

[0070] FIG. 22 is an isometric view of the inner side of a door guide of the door assembly of FIG. 16; and

[0071] FIG. 23 is an isometric view of the outer side of the door guide of FIG. 22.

[0072] While the present invention is amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit the present invention to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present invention.

DETAILED DESCRIPTION

[0073] For purposes of this application, relative direction may be described in terms of “x” and “y” and “z” directions, and these designations relative to the parts of the container are intended to be in accordance with the directional key provided as a part of FIGS. 1, 13 and 14.

[0074] Referring now to FIG. 1, a front opening wafer container 20 generally includes an enclosure portion 22 and a front door 24. Enclosure portion 22 generally includes top wall 26, bottom wall 27, side walls 28, 30, back wall 32, and door frame 34 defining a front opening 36. In addition, latch bolt recesses 56 are defined in each of top side 42 and bottom side 46 of door frame 34. Each latch bolt recess 56 is surrounded by raised portion 58. Outwardly facing interlock groove 55 is defined at inner edge 57 of door frame 34. Wafer support structure 60 may be provided inside enclosure portion 22 for receiving wafers in a plurality of slots 62. A robotic lifting flange 64 and a kinematic coupling 66 as are known in the art may be provided on the top and bottom outer surfaces respectively of enclosure portion 22.

[0075] Front door 24 generally includes body portion 68 presenting rear side 70, front side 72, top peripheral face 74, side peripheral faces 76, 78, and bottom peripheral face 80. A pair of latch recesses (not depicted) are defined in front side 72, and are covered by front panel 82. Each latch recess receives a latching mechanism (not depicted), operable by a key insertable though key apertures 84 in front panel 82 to selectively extend and retract latch bolts 86 to engage in latch bolt recesses 56 of container portion 22 to secure front door 24 in door frame 34. The latch mechanisms can be generally configured as disclosed in U.S. Pat. Nos. 4,995,430; 7,182,203; or 7,168,587, all of which are owned by the owner of the instant application, and all of which are hereby incorporated herein by reference.

[0076] In an embodiment depicted in FIG. 2, front door 24 includes wafer cushion member 87 having wafer cushion 88 with a plurality of wafer engaging portions 90. Wafer cushion member 87 is positioned on rear side 70 of body portion 68 with gasket member 92 interposed between the two. Notably, wafer cushion member 87 covers substantially the entirety of rear side 70 in the depicted embodiment. Wafer cushion 88 is received in recess 92 formed in body portion 68, with recess 92 extending from the top of the door to the bottom of the door and is centrally positioned with respect to the left and right sides of the door. The recess has different depths, with the deepest portion extending along the vertical mid-line of recess 92. Wafer cushion member 87 defines forwardly projecting lip 89 around its entire periphery.

[0077] Referring to FIG. 3, an alternative embodiment of front door 24 is depicted. Gasket frame assembly 94 generally includes gasket frame 96, and gasket 98. Gasket 98 can be either separately formed from gasket frame 96 as depicted, or over-molded on gasket frame 96 using commonly known over-molding techniques. Gasket frame 96 defines forwardly projecting lip 97 around its entire periphery. Wafer cushion member 100 is separate from gasket frame assembly 94 and includes wafer cushion 88 with a plurality of wafer engaging portions 90. Wafer cushion member 100 is sandwiched between gasket frame assembly 94 and body portion 68. Again, wafer cushion 88 is received in recess 92 formed in body portion 68.

[0078] FIG. 4 depicts, in fragmentary cross-section, front door 24 fully engaged in door frame 34. Forwardly projecting lip 89 of wafer cushion member 87 is received in generally v-shaped interlock groove 55 of door frame 34, with sloped engagement surface 89a of lip 89 abutting sloped engagement surface 55a of interlock groove 55. Gasket member 92, which is sandwiched between wafer cushion member 87 and body portion 68, has projecting portion 202, which includes laterally projecting lip 204. Lip 204 engages and seals with side wall 205 of door frame 34. It will be appreciated that inwardly facing surface 206 of wafer cushion member 87 can be angled at a slightly different angle from outwardly facing surface 208 of body portion 68 to compress gasket member 92 and provide a clamping force in order to better secure gasket member 92 in place and prevent any slippage or dislocation of gasket member 92.

[0079] It will be appreciated that that the abutting engagement of sloped surface 55a and sloped surface 89a forms an interlock between front door 24 and container portion 22, tending to resist outward deflection of top wall 26, bottom wall 27, side walls 28, 30, door frame 34, and front door 24. For example, when container 20 is loaded with wafers and lifted with robotic lifting flange 64, the weight of the wafers will apply a force tending to deflect top wall 26 and bottom wall 27 away from each other, especially at front opening 36. With front door 24 engaged in door frame 34 as depicted in FIG. 4, the engagement of forwardly projecting lip 89 of wafer cushion member 87 in interlock groove 55 enables door 24 to be loaded in tension, thereby resisting deflection of top wall 26 and bottom wall 27.

[0080] FIGS. 8-10 depict front door 24 in successive stages of engagement in door frame 34. In FIG. 8, front door 24 is registered with door frame 34 with projecting portion 202 of gasket member 92 inside outer edge 54 of door frame 34. As front door 24 is advanced into door frame 34 as depicted in FIG. 9, the leading edges of wafers 210 engage lower sloped surfaces 212 of wafer engaging portions 90, causing wafers to ride upward. Projecting portion 202 begins to engage with side wall 205 of door frame 34. In FIG. 10, as front door 24 is advanced into full engagement in door frame 34, the edges of wafers 210 seat in the v-shaped wafer engaging portions 90. Forwardly projecting lip 89 of wafer cushion member 87 is received in interlock groove 55, with sloped surface 89a of lip 89 abutting sloped surface 55a of interlock groove 55. Lip 204 engages and seals against side wall 205 of door frame 34, thereby sealing the interior of enclosure portion 22 and wafers 210 from outside contaminants.

[0081] As depicted in FIGS. 5-7, wafer cushion member 87 can be secured to rear side 70 of body portion 68 with a plurality of engagement structures 214 disposed on rear side 70 proximate each of side peripheral faces 76, 78, that engage corresponding hooks 216 on wafer cushion member 87. If desired, additional engagement structures 218 can be provided nearer the lateral midpoint of rear side 70, engagable with correspondingly disposed hooks on wafer cushion member 87, to further secure wafer cushion member 87 in place.

[0082] Another advantageous aspect of wafer cushion member 87 in certain embodiments of the invention is depicted in FIGS. 2 and 11. Each wafer engaging portion 90 of wafer cushion 88 is resilient and serves as a spring, when the wafers are fully engaged, to apply limited force to each wafer so as to hold the wafers in place and cushion the wafers against physical shock. According to the depicted embodiment, each wafer engaging portion 90 has a ramped protrusion 220 proximate the outboard edge. This ramped protrusion 220 is disposed proximate the latch mechanisms 222 of front door 24 when wafer cushion member 87 is disposed on body portion 68. The top side of ramped protrusion 220 is the first point of contact for wafers 210 as front door 24 is advanced into door frame 34. As more force is applied by each wafer 210 to wafer engaging portion 90, the wafer engaging portions 90 deflect. Since initial contact occurs at ramped protrusions 220, more of the cushion loading due to the force applied by the spring action of wafer engaging portions 90 is applied to body portion 68 along latching mechanisms 222, where front door 24 is more able to resist outward deflection due to the engagement of latch bolts 86 in latch bolt recesses 56. Consequently, distortion of container 20 from the cushion loading is relatively minimized. It will be appreciated that, in other embodiments, the first point of initial contact of wafers 210 with the bottom edge of ramped protrusion 220 to achieve the same effect.

[0083] Another advantageous aspect of certain embodiments is provided by the raised portions 58 around each of the latch bolt recesses 56. These raised portions 58, coupled with the slight outward slope of side wall 205 of door frame 34, enable front door 24 to be spaced apart from door frame 34, especially at outer edge 35. In use, when front door 24 is removed and replaced in door frame 34, there may be movement of air inwardly into enclosure portion 22 due to the hermitic seal. The larger clearance provided by spacing front door 24 further away from door frame 34 may cause the velocity of the air to be reduced from what it would otherwise be, thereby reducing the likelihood that particulates will be entrained in the air and carried into enclosure portion 22 to contaminate the wafers inside. Further, the raised portions 58 can minimize the clearance between front door 24 and door frame 34 at the latch locations, thereby minimizing the unsupported length of latch bolts 86 when they are engaged in latch bolt recesses 56, and reducing possible distortion of front door 24 in the “z” direction.

[0084] Referring to FIG. 12, an alternative embodiment is depicted that has front door 102 engaged in door frame 104 of container portion 106. Latch members 108 extend and retract into receivers 109 on door frame 104 to removably secure the door in the door frame. Sealing member 110 or gasket has elastomeric body 113 with retained portion 111 that is retained by being sandwiched between frame or base portion 117 of the door and inner retention frame 120. Elastomeric body 113 also has non-retained and outwardly extending portion 112. Outwardly extending portion 112 has radially extending portion 116 and axially extending portion 114. Positioned on the container portion side of the seal is strip portion 130 formed of a different material, preferably a polymeric material, that may be non-elastomeric and extends, in a radial perspective, outwardly from the inner retention frame, where it may be adhered thereto, onto the inwardly facing (toward the container portion) vertical face 136 of elastomeric gasket 110, and then angles inwardly and is adhered to angled inward face 140 of the elastomeric gasket for insertion in recess 144. The strip portion may form a door frame engagement portion to primarily or exclusively contact the door rather than the elastomeric body portion. The door frame engagement strip portion 130 extends circumferentially around the inside perimeter of the door frame and engages with the outwardly extending angled protrusion 148 of door frame 104. As depicted, the strip portion may conform to the shape of the door frame where it engages. The elastomeric body and the door frame engagement strip portion define sealing portion 150. The door frame engagement strip portion may be formed from a rigid and resilient strip of polymer material and preferably extends endlessly around the door and is adhered to the elastomeric gasket material such as by over-molding. The engagement strip portion can form the entirety of the engagement of the sealing portion with the door or a portion of the elakomeric gasket can also directly contact and seal with the door. The engagement strip portion can thus provide a sealing engagement that adheres less to the door frame providing for easier removal of the door as compared to the elastomeric gasket material.

[0085] FIG. 12 also illustrates a further embodiment of the securement of the gasket 111 between the inner retention frame 120 and base portion 117 of the door. The frame 120 clamps on to an inwardly extending (towards the container portion) protrusion 160 of the door base portion 117 with sealing member 110 also sandwiched between the frame and protrusion at recess 164 in frame 120, and also being compressed therein. Although only a cross section is illustrated at the top of the door, the interfacing components and features, such as the sealing member, strip portion, protrusion, recess, preferably extend the around the entirety of the outer periphery of the door and inner periphery of the door frame.

[0086] It will be appreciated that any or all of the components of wafer container 20 may generally be injection molded from polymers typically used for semiconductor wafers. Such materials include, but are not limited to, polycarbonates, fluoropolymers, and polyetheretherketone.

[0087] A wafer container 300 according to another embodiment of the present invention is depicted in FIGS. 13-23, and generally includes enclosure portion 302 and door 304. Enclosure portion 322, as depicted in FIGS. 13 and 14 generally includes bottom wall 306, top wall 308, side walls 310, 312, back wall 314, and door frame 316 on the front side of the enclosure defining an opening 318 for receiving door 304. Ramped portions 320 are defined on the inner periphery of door frame 316 proximate the mid-point of each side 322, 324, 326, 328, of the door frame 316, each sloping toward the outer edge 330 in the “z” axis direction as annotated in FIG. 13. Adjacent and inwardly from each ramped portion 320, an elongate projection 332 extends outwardly in the “z” axis direction, defining a generally v-shaped recess 334 extending parallel to outer edge 330 of door frame 316. In addition, latch bolt recesses 336 are defined in each of bottom side 322 and top side 328 of door frame 316. Each latch bolt recess 336 is surrounded by a raised portion 338. A wafer support structure (not depicted) may be provided inside enclosure portion 302 for receiving wafers (not depicted) in a plurality of slots defined in the structure. A robotic lifting flange 340 and a kinematic coupling 342 are known in the art may be provided on the top and bottom outer surfaces respectively of enclosure 302.

[0088] Door 304 as depicted in FIGS. 13-23 generally includes body portion 344 presenting rear side 346, front side 348, top peripheral face 350, side peripheral faces 352, 354, and bottom peripheral face 356. A pair of latch recesses (not depicted) are defined in front side 348, and are covered by front panel 358. Each latch recess receives a latching mechanism (not depicted), operable by a key insertable though key apertures 360 in front panel 358 to selectively extend and retract latch bolts 361. Wafer cushion 500 is disposed on rear side 346.

[0089] According to an embodiment of the invention, each of top peripheral face 350, side peripheral faces 352, 354, and bottom peripheral face 356 defines a door guide recess 362. The recesses 362 in top peripheral face 350 and bottom peripheral face 356 are centered on vertical door centerline 364, while recesses 362 in the side peripheral faces 352, 354, are centered on horizontal door centerline 366.

[0090] Each door guide recess 362 is defined by inner wall 368, side walls 370, 372, and bottom wall 374 as depicted in FIG. 20. Groove 376 is defined in each of side walls 370, 372, and bottom wall 374, and extends around the periphery of the recess 362. Bottom wall 374 also defines guide engagement apertures 378, 380, and central guide engagement aperture 379. A pair of guide tabs 382 extend outwardly from inner wall 368 proximate each end of the recess 362.

[0091] Body portion 344 may also define corner door guide receiving recesses 384 at each of the corners 386, 388, 390, 392, of door 304. Each recess 384 can receive a corner door guide (not depicted) as is known in the art to assist in locating door 304 in door frame 316.

[0092] Door guide 394 is depicted in Figures and generally includes a unitary elongate body portion 396 formed from polymer material having a low coefficient of friction and favorable low particle generating characteristics, such as mixture of PBT or Acetal. Tabs 398 extend laterally outward from each end 400, 402. Ribs 404 are provided on bottom edge 406, and the central rib 404 includes central locating tab 408. Engagement tabs 410 extend downwardly proximate each end 400, 402, and include detent 412. Inner side 414 also has a wedge shaped projection 416 defined proximate each end 400, 402, each projection 416 defining groove 418. Top edge 420 is defined in a generally U-shaped opening between legs 422, 424. The sides 426 of the U-shaped opening may be slightly inclined as depicted.

[0093] One of door guides 394 is removably received in each of door guide recesses 362 in top peripheral face 350, side peripheral faces 352, 354, and bottom peripheral face 356, of body portion 344. Door guide 394 is inserted by registering each of grooves 418 with one of guide tabs 382 and advancing the door guide downwardly as depicted in FIG. 21. As guide 394 is advanced downward, tabs 398 are received and slide in the groove 376 defined in each of side walls 370, 372. Once guide 394 is fully inserted, ribs 404 are received in groove 376 in bottom wall 374 with central locating tab 408 extending through central guide engagement aperture 379. Engagement tabs 410 are received through guide engagement apertures 378, 380, and detent 412 engages behind bottom wall 374 to secure guide 394 in position. With guide 394 in position, guide surfaces 428 face outwardly.

[0094] Door 304 is engaged in door frame 316 of enclosure portion 302 by registering door 304 with the opening defined by door frame 316 as depicted in FIG. 13. As door 304 is advanced into frame 316, guide surfaces 428 of door guides 394, engage and slide on ramped portions 320 on the inner periphery of door frame 316. The slight slope of ramped portions 320 helps guide door 304 into the desired position. Moreover, the inclined edges 426 of the U-shaped opening defining top edge 420 may also assist in locating and centering door 304 in door frame 316 in the “x” and “y” directions. Once door 304 is fully engaged in frame 316, the latch mechanisms can be actuated to move latch bolts 361 into latch bolt recesses 336 to secure door 304 in place.

[0095] As depicted in the cross-sectional view of FIG. 19, with door 304 in the fully engaged position in frame 316, top edge 420 of guide 394 engages in recess 334. Top edge 420 may be seated in recess 334, that is in contact and engagement, or may be separated and not in direct contact. Elastomeric gasket 430, received in recess 431 on door 304, engages with shoulder 432 on door frame 316 to provide hermetic sealing of the container. The engagement of top edge 420 of guide 394 in recess 334, may serve to “interlock” door 304 in frame 316, to inhibit unintended disengagement of door 304, and damage to the integrity of the hermetic seal occurring due to mechanical shocks to the container. Further, it will be appreciated that the abutting engagement of sloped engagement surface 434 on top edge 420 of door guide 394 with sloped engagement surface 436 in recess 334 may form an interlock between door 304 and container portion 302, tending to resist outward deflection of top wall 308, side walls 310, 312, bottom wall 306, door frame 316, and door 304. For example, when container 300 is loaded with wafers and lifted with robotic lifting flange 340, the weight of the wafers will apply a force tending to deflect top wall 308 and bottom wall 306 away from each other, especially at front opening 318. With door 304 engaged in door frame 316 as depicted in FIG. 19, the engagement of forwardly projecting top edge 420 of door guide 394 in recess 334 enables door 304 to be loaded in tension, thereby resisting deflection of top wall 308 and bottom wall 306.

[0096] Still further, it is believed that the central positioning of door guides 394 on top peripheral face 350 and bottom peripheral face 356 on vertical door centerline 364, the central positioning of door guides 394 on the side peripheral faces 352, 354, on horizontal door centerline 366 serve to better locate and position door 304 in the “x”, “y” and “z” directions than previously known corner door guides alone. It will be appreciated that the door guides 394 according to embodiments of the present invention may be used alone without corner guides or in conjunction with corner guides if desired to give additional positioning accuracy.

[0097] Another advantageous aspect of certain embodiments is provided by the raised portions 338 around each of the latch bolt recesses 336. These raised portions 338, coupled with the slight outward slope of side wall 490 of door frame 316 around its entire periphery, enable door 304 to be spaced apart from door frame 316, especially at outer edge 330. In use, when door 304 is removed and replaced in door frame 316, there may be movement of air inwardly into enclosure portion 302 due to the hermetic seal. The larger clearance provided by spacing door 304 further away from door frame 316 may cause the velocity of the air to be reduced from what it would otherwise be, thereby reducing the likelihood that particulates will be entrained in the air and carried into enclosure portion 302 to contaminate the wafers inside. Further, the raised portions 338 can minimize the clearance between door 304 and door frame 316 at the latch locations, thereby minimizing the unsupported length of latch bolts 361 when they are engaged in latch bolt recesses 336, and reducing possible distortion of door 304 in the “z” direction.

[0098] The foregoing descriptions present numerous specific details that provide a thorough understanding of various embodiments of the invention. It will be apparent to one skilled in the art that various embodiments, having been disclosed herein, may be practiced without some or all of these specific details. In other instances, components as are known to those of ordinary skill in the art have not been described in detail herein in order to avoid unnecessarily obscuring the present invention. It is to be understood that even though numerous characteristics and advantages of various embodiments are set forth in the foregoing description, together with details of the structure and function of various embodiments, this disclosure is illustrative only. Other embodiments may be constructed that nevertheless employ the principles and spirit of the present invention. Accordingly, this application is intended to cover any adaptations or variations of the invention.

[0099] For purposes of interpreting the claims for the present invention, it is expressly intended that the provisions of Section 112, sixth paragraph of 35 U.S.C. are not to be invoked unless the specific terms “means for” or “step for” are recited in a claim.